1. Field of the Invention
This invention generally relates to a copying machine and particularly to a copying machine which uses a photosensitive belt. More specifically, the present invention relates to a copying machine using a cassette type photosensitive belt which may be detachably installed.
2. Description of the Prior Art
Copying machines using cassette type photosensitive belts or webs are well known in the art. For example, as disclosed in the Japanese Patent Pub. No. 49-22660 and Utility Model Laid-open Pub. No. 50-31935, in the prior art machines, use has been made of a significantly long photosensitive belt extended between a pair of spools. With such a structure, the belt may be used for a long period of time and thus the need for replacement arises less frequently. However, since the photosensitive belt is significantly long, the diameter of the belt when wound around the spool is relatively large, thereby making the cassette larger in size and producing a loss in time required for rewinding or change in direction of the cassette. Moreover, since the diameter of the belt wound around the spool changes significantly between the start and the end of operation, it is required to specially provide a constant speed driving device or feed-back device for constant speed motion for moving the photosensitive belt always at constant speed from the supply spool to the take-up spool, which tends to complicate the structure.
Prior art copying machines using relatively short photosensitive belts are disclosed, for example, in Japanese Patent Pub. No. 52-80843, Utility Model Pub. No. 53-50441 and Patent Laid-open Pub. No. 49-44756. However, in these prior art machines, the cassette is comprised of two separate bodies or the photosensitive belt must be directly set in position, so that handling of the photosensitive belt is poor and replacement of photosensitive belts is cumbersome. Besides, in association with the movement of the photosensitive belt, other elements such as take-up roller and charger must also be moved, so that the layout of various elements of a copier is rather limited, thereby making the machine complicated in structure and hindering to attain a high speed operation.